1. Field of the Invention
The present invention relates to an expansion valve, and more particularly to an expansion valve suitable for use in a refrigeration cycle.
2. Description of the Related Art
A refrigeration cycle in an automotive air conditioner generally includes a compressor for compressing a circulating refrigerant, a condenser for condensing the compressed refrigerant, an expansion valve for throttling and expanding the condensed refrigerant and delivering the resulting spray of refrigerant, and an evaporator for cooling the air in a vehicle interior using evaporative latent heat of the refrigerant. The expansion valve controls the flow rate of the refrigerant delivered toward the evaporator so that the refrigerant having passed through the evaporator has a predetermined degree of superheat.
In such a refrigeration cycle, sufficient condensing may not be achieved during low-load operation, for example. This may result in a gas-liquid two-phase state of the high-pressure refrigerant flowing into the expansion valve, and cause a phenomenon of liquid refrigerant and gas refrigerant intermittently passing through a valve section. In this case, the liquid refrigerant (liquid phase), which has a relatively high density, flows less smoothly depending on the layout of piping connecting the evaporator and the expansion valve. As a result, liquid stagnation may occur at a particular position in the piping and a subsequent flow of refrigerant hitting the liquid stagnation may cause noise.
To address such circumstances, a structure in which a throttle passage downstream of a valve section of an expansion valve is proposed, for example (refer to Japanese Patent Application Publication No. 2011-245549, for example). Specifically, a plate having a small hole at the center is disposed in a downstream-side passage in the valve section. This structure is proposed to make bubbles of the refrigerant finer through two stages of pressure reduction by the valve section of the expansion valve and by the throttle passage, so as to reduce noise (breakage sound) caused by the bubbles breaking while the refrigerant passes through the liquid stagnation.